HSRP on both sides of the Router.

[Adnan_Siddiqi]

Hello All ,

We have scenario where  we want to have redundancy on Routers on which SIP  is terminating via ITSP on Ethernet. The ITSP is giving us traffic on an our IP  and we are handing over them to their IP a /28 subnet.

Just wanted to know if we run HSRP on both routers to have redundancy on router level as link is only one. Is this ok or a better design can be made . Attached is diagram for your reference

Router A

interface GigabitEthernet0/0/0

Desc  inside interface

ip address  yyyyy /24

duplex auto

speed auto

standby 0 ip yyyyyy.A

standby priority 150

standby preempt

!

interface GigabitEthernet0/0/1

Desc out side interface

ip address  XXXXXXXXXXX.A /28

duplex auto

speed auto

standby 1 ip  YYYYYYY. B

standby 1 priority 150

standby 1 preempt

.

Router B :

interface GigabitEthernet0/0/0

Desc  inside interface

ip address

duplex auto

speed auto

standby 0 yyyyyy.B

!

interface GigabitEthernet0/0/1

Desc  out side

ip address

duplex auto

speed auto

standby 1 ip YYYYYYY. A

Thanks in anticipation

ADNAN

[Richard Burts]

Adnan

HSRP is appropriate to provide redundancy and what you show in your drawing seems a good example of its use. I do wonder about the difference in priority between the active router and the standby router. Though since you are not doing any kind of track perhaps it does not make any real difference.

I wonder whether you might want to set it up so that if there is failover to the standby on the outside interface that it also triggers a failover to the inside interface also? This would need some kind of track to be implemented.

HTH

Rick

[Adnan_Siddiqi]

Thanks Richard ,

Planning to use Router 1 as primary so it has higher priority , since the all links ( ethernet connections)  are internal except the one coming from ITSP for sending and receiving  SIP traffic  so have not done any tracking . The chance of any internal link going down are very rare as all equipment is located in a Data center Closet.

@paul driver  : No natting or any kind of routing is being done as we just have to handover the SIP traffic to our SIP provider and receive the same for them . We are not going on the internet so all addresses are also private .

Waiting to hear from you people the final words   .. Thanks for your kind consideration earlier.

[paul driver]

Hello

apologies interpreted the picture completely wrong I saw the inside - outside   

and assumed nat 

regards your topology what routing protocols are you using 

[Richard Burts]

Adnan

Your comment about all the links being internal made me think more about your environment and to take a closer look at your diagram. I had not thought about it so much in my original response but now am realizing that both routers go through a common switch to communicate with the same internal lan and that both routers go through a common switch to get to the same provider. Most of the time when we use HSRP there is an independent path to the outside or to the inside. In that case if there is a problem with one of the paths or with one of the routers, then the surviving router can provide connectivity. But in your case if there is a problem with the lan or a problem with the provider then having a second router does not help you get around the problem. The redundancy provided in your diagram protects you only against failure of one of the routers. If you and your management believe that this protection is worth the effort then HSRP would work. But I wonder if the benefit you get is worth the effort and the expense of having the second router.

HTH

Rick

[Adnan_Siddiqi]

Hi Richards ,

You are right , current purpose is to add redundancy to active router . We are asking management and the ITSP to arrange another link to have links redundancy as well on outside ( ITSP side) . Then we will add interface tracking as well.

As I was not able to find any thread in which HSRP is working on both sides of the router was discussed.

Adnan

[Richard Burts · Accepted solution]

Adnan

If the purpose of your question was to verify the possibility of HSRP operating on both sides of the router the answer is absolutely it does work. And from a technical perspective it would work in your environment. But from a practical perspective you would gain very little benefit from running HSRP on both sides in your current environment.

HTH

Rick

[Richard Burts]

Adnan

I am glad that our suggestions have been helpful to you. Thank you for marking tis question as solved. This will help other participants in the community to identify discussions which have helpful information. These communities are excellent places to ask questions and to learn about networking. I hope to see you continue to be active in the communities.

While there were some technical things discussed I believe that the most important part of the discussion was to recognize the differences between what is technically possible to implement and what adds actual value to your network.

HTH

Rick

[paul driver]

Hello

Adding to ricks comments, looks like you are also using nat so you need to also accommodate for the translation.

If you dont track hrsp its possible you could end with asymmetric routing as such hrsp has transitioned but the bgp return path is still hitting the old hrsp primary router and as nat isn't stateful the router which is now not performing nat would have an empty nat table which could end up with loss of connectivity.

Two ways you can accommodate this would be the use redundancy NAT with hrsp or Statefull nat with hrsp